Use of catalysts such as nickel for hydrogenation of oils in the edible oil industry is well known. A liquid oil or blend of oils from animal and vegetable sources is hydrogenated by exposure to hydrogen in the presence of a catalyst in order to change its physical properties and appearance. Typically such catalysts are in the form of a powder or similar solid which is suspended in or otherwise exposed to the oil. As a result of oxidation and other chemical changes in the catalyst, its usefulness as a catalyst will decrease over time, until it is no longer a viable catalyst. It is necessary to dispose of the spent catalyst that is generated by the system. Such oil-containing spent catalyst is presently placed in landfills or recovered by methods that allow recovery of the catalyst but do not allow recovery of the oil.
Because of economic considerations, it is desirable to recover and recycle the oil which is in the spent catalyst, as well as the catalyst itself. U.S. Pat. No. 5,008,001 discloses a method for recovering and recycling both the catalyst and the oil from a slurry containing spent catalyst. The method of 5,008,001 optionally includes the use of conventional solid-liquid separation to produce a catalyst cake and specifically includes heat drying of the oil containing catalyst slurry or cake to remove the oil and produce catalyst which is substantially free of oil. The oil removed in the heat drying process is recovered.
U.S. Pat. No. 4,277,316 discloses a solvent extraction process wherein solvents are separated from a solvent bearing material by distillation. The desired solvents are removed by the application of heat which is generated by the combustion of the noncondensable fraction of those solvents, while the condensable fraction is condensed and removed for storage. Following removal of the desired solvents at one predetermined temperature, the mixture is heated to a second predetermined temperature to remove the remaining organic materials, thereby leaving a residue which is substantially free of oil and can be removed from the container. The process is a batch process.
U.S. Pat. No. 4,395,315 discloses a method for removing nickel from a waste material containing organic material and small amounts of iron or aluminum. The method includes removing the organic impurities from the waste mixture by either calcining or washing in a Stoddard solvent, and leaching the resulting material with an acid. The method of 4,395,315 does not provide for recovery of the organic material.
The present invention discloses a method and apparatus for recovery of both oil and catalyst from a spent catalyst. The method of the present invention is economically efficient and environmentally sound and uses a relatively small amount of energy to recover usable oil from the spent catalyst. These and other advantages of the present invention will become apparent in the description below.